The present invention is directed to method and apparatus for moving molten metal ladles between a cover position, a ladle-load position and a pouring position at a casting station. More particularly, a method and an apparatus are taught which enhance a pressure casting process to expedite the movement from the pouring station of a molten-metal evacuated ladle and the positioning of a molten-metal filled ladle at the pouring station without the intermediate delays associated with ladle covering and uncovering.
Casting and casting practices generally involve the use of molten metals at elevated temperatures. This molten metal practice requires the use of heavy apparatus for the holding and transport of the metal. Specifically, molten metal for casting is frequently held in large steel or cast-iron ladles lined with refractory brick. In a pressure-casting or pouring operation, the ladle is placed in a pouring tank and a tank cover is placed atop the pouring tank. This tank cover is equipped with a pouring tube as well as ports to elevate the gas pressure above the molten metal. Avoidance of fracture of the pouring tube and refractory linings generally involves maintaining or preheating the pouring tank cover and pouring tube. A holding or heating furnace is frequently utilized for this purpose. However, the physical act of positioning the pouring tank cover atop the pouring tank and thereafter securing the pouring tank cover are time-consuming operations and an inhibition to a rapid production operation.
A presently known operation utilizes a single pouring or casting station in cooperation with twin ladle-loading stations. These ladle-loading stations use pressure-pouring tanks on transfer cars for holding the hot-metal ladles, and for transporting the ladles between the ladle-loading stations and the pouring station. In this operation, a ladle of molten metal is transported to a pressure-pouring tank at a ladle-loading station for subsequent transfer of the ladle containing pouring tank to the pouring station. At the pouring station, a pressure-pouring tank cover is positioned on and secured to the pressure pouring tank by the pouring crane. After pouring of the molten metal from the ladle, the pressure pouring tank cover is removed using the pouring crane. The pressure pouring tank is then transported to the first ladle-loading station for eventual filling with another ladle of molten metal. A second molten-metal-filled ladle in a pressure pouring tank is then transported to the pouring station from the second ladle-loading station and a pressure pouring tank cover is positioned and secured to the second pressure pouring tank at the pouring station, as described above.
The time delays in pressure pouring tank covering and the use of the pouring crane at the pouring station are significant when measured in terms of daily lost production of large castings. Accordingly, it is an object of the present invention to provide a more efficient pressure pouring arrangement.
The present invention provides a method and apparatus to provide a more efficient arrangement for bottom-pressure casting. In this method, the pressure pouring tank cover is secured on a first pressure pouring tank at a ladle-load station prior to moving the covered pressure pouring tank with a full ladle into the pouring-station position. Further, subsequently but prior to the emptying of the first ladle, a second metal-filled ladle in a second pressure pouring tank is positioned in a second ladle-load station with its pressure pouring tank cover secured. The second covered pressure pouring tank is ready for immediate movement into the pouring station after emptying of the first ladle and the removal of the first pouring tank from the pouring station without removal of the first pressure pouring tank cover. The pressure pouring tank covers are moved onto the pouring tanks at the ladle-load stations by a jib crane or overhead crane. The pressure pouring tank covers with their pouring tubes are maintained at an elevated temperature at cover station ovens within the range of motion of the jib crane or overhead crane. The second pressure pouring tank is available for immediate placement into the pouring station to continue production as soon as the first pressure pouring tank with its empty ladle has been moved a distance adequate to provide the necessary clearance for the second pressure pouring tank transfer-car bearing a second metal-filled ladle.